The present invention relates to an image display apparatus which allows observation of one combined image of plural images formed by light fluxes from plural image-forming elements from an exit pupil position, and more particularly to an image display apparatus suitable for a head mounted display (HMD) or the like.
The image display apparatus such as an HMD is required to be capable of displaying a high quality image with a wide viewing angle. In order to increase the viewing angle, a large LCD panel or the like is preferably used as an image-forming element which forms an original image. In many cases, however, it is difficult to obtain an image-forming element compliant with necessary viewing angle specifications.
Under such circumstances, Japanese Patent Laid-Open No. 07-274097, Japanese Patent No. 3524569, and Japanese Patent Laid-Open Nos. 11-326820 and 10-246865 disclose image display apparatuses each of which uses plural compact image-forming elements, forms images in mutually different viewing angle areas with light fluxes from the image-forming elements, and allows observation of a combined image formed by joining the images to each other.
Each of the image display apparatuses disclosed in Japanese Patent Laid-Open No. 07-274097 and Japanese Patent No. 3524569 includes an optical system in which a V-shaped mirror is disposed symmetrically with respect to a visual axis of an observer. In this image display apparatus, a light flux from an original image formed by a first image-forming element is reflected by one reflection surface of the V-shaped mirror to be introduced to an exit pupil while a light flux from an original image formed by a second image-forming element is reflected by another reflection surface of the V-shaped mirror to be introduced to the exit pupil.
The image display apparatus disclosed in Japanese Patent Laid-Open No. 11-326820 uses a prism having a shape symmetrical with respect to a visual axis. In this image display apparatus, a light flux from an original image formed by a first image-forming element is introduced to the prism to enter thereinto through a first surface thereof facing the first image-forming element, is reflected by second and third surfaces of the prism which are internal total reflection surfaces also serving as transmission surfaces, and is then transmitted through the second surface to be introduced to an exit pupil.
Further, a light flux from an original image formed by a second image-forming element is introduced to the prism to enter thereinto through a fourth surface thereof facing the second image-forming element, is reflected by fifth and sixth surfaces of the prism which are internal total reflection surfaces also serving as transmission surfaces, and is then transmitted through the fifth surface to be introduced to the exit pupil.
The image display apparatus disclosed in Japanese Patent Laid-Open No. 10-246865 also uses a prism having a shape symmetrical with respect to a visual axis. In this image display apparatus, light fluxes from original images formed by first and second image-forming elements enter the prism through first and second surfaces thereof respectively facing the first and second image-forming elements. The first and second surfaces are also used as reflection surfaces for reflecting the light fluxes entering the prism through the first and second surfaces to introduce them to an exit pupil.
However, in all the image display apparatuses disclosed in Japanese Patent Laid-Open No. 07-274097, Japanese Patent No. 3524569, and Japanese Patent Laid-Open Nos. 11-326820 and 10-246865, the two image-forming elements are used for one exit pupil, that is, one eye of an observer. As a result, in the image display apparatus such as an HMD generally used for both eyes, four image-forming elements are necessary, which causes not only complication and enlargement of the apparatus but also a cost increase.